Dell E156FPc - No Backlight Troubleshooting

Dell E156FPc
44
No Backlight
Check C201 (+) =12V
NG
OK
Check F902
Check ON/OFF signal
Check Interface board
NG
OK
Check IC201 pin9=12V ?
NG
OK
Change Q201 or Q202
Check the pin1 of IC201 have saw tooth wave
NG
OK
Change IC201
Check D201 (-) have the output of square wave at short time.
NG
OK
Check Q203/Q204/Q205/D201
Check the resonant wave of pin1 & pin6 for PT201
NG
Check the output of PT201
Check Q206/Q207/C221
Check connecter & lamp
OK
NG
Change PT201
OK